Suberoylanilide hydroxamic acid reversed cognitive and synaptic plasticity impairments induced by sevoflurane exposure in adult mice

Minocycline Attenuates Sevoflurane-Induced Postoperative Cognitive Dysfunction in Aged Mice by Suppressing Hippocampal Apoptosis and the Notch Signaling Pathway-Mediated Neuroinflammation

Postoperative cognitive dysfunction (POCD), an important postoperative neurological complication, is very common and has an elevated incidence in elderly patients. Sevoflurane, an inhaled anesthetic, has been demonstrated to be associated with POCD in both clinical and animal studies. However, how to prevent POCD remains unclear. Minocycline, a commonly used antibiotic can cross the blood-brain barrier and exert an inhibitory effect on inflammation in the central nervous system. The present work aimed to examine the protective effect and mechanism of minocycline on sevoflurane-induced POCD in aged mice. We found that 3% sevoflurane administered 2 h a day for 3 consecutive days led to cognitive impairment in aged animals. Further investigation revealed that sevoflurane impaired synapse plasticity by causing apoptosis and neuroinflammation and thus induced cognitive dysfunction. However, minocycline pretreatment (50 mg/kg, i.p, 1 h prior to sevoflurane exposure) significantly attenuated learning and memory impairments associated with sevoflurane in aged animals by suppressing apoptosis and neuroinflammation. Moreover, a mechanistic analysis showed that minocycline suppressed sevoflurane-triggered neuroinflammation by inhibiting Notch signaling. Similar results were also obtained in vitro. Collectively, these findings suggested minocycline may be an effective drug for the prevention of sevoflurane-induced POCD in elderly patients.

Epigenetic Mechanisms of Postoperative Cognitive Impairment Induced by Anesthesia and Neuroinflammation

Cognitive impairment after surgery is a common problem, affects mainly the elderly, and can be divided into postoperative delirium and postoperative cognitive dysfunction. Both phenomena are accompanied by neuroinflammation; however, the precise molecular mechanisms underlying cognitive impairment after anesthesia are not yet fully understood. Anesthesiological drugs can have a longer-term influence on protein transcription, thus, epigenetics is a possible mechanism that impacts on cognitive function. Epigenetic mechanisms may be responsible for long-lasting effects and may implicate novel therapeutic approaches. Hence, we here summarize the existing literature connecting postoperative cognitive impairment to anesthesia. It becomes clear that anesthetics alter the expression of DNA and histone modifying enzymes, which, in turn, affect epigenetic markers, such as methylation, histone acetylation and histone methylation on inflammatory genes (e.g., TNF-alpha, IL-6 or IL1 beta) and genes which are responsible for neuronal development (such as brain-derived neurotrophic factor). Neuroinflammation is generally increased after anesthesia and neuronal growth decreased. All these changes can induce cognitive impairment. The inhibition of histone deacetylase especially alleviates cognitive impairment after surgery and might be a novel therapeutic option for treatment. However, further research with human subjects is necessary because most findings are from animal models.

The Mechanisms of Sevoflurane-Induced Neuroinflammation

Sevoflurane is one of the most commonly used inhaled anesthetics due to its low blood gas coefficient, fast onset, low airway irritation, and aromatic smell. However, recent studies have reported that sevoflurane exposure may have deleterious effects on cognitive function. Although neuroinflammation was most widely mentioned among the established mechanisms of sevoflurane-induced cognitive dysfunction, its upstream mechanisms have yet to be illustrated. Thus, we reviewed the relevant literature and discussed the most mentioned mechanisms, including the modulation of the microglial function, blood–brain barrier (BBB) breakdown, changes in gut microbiota, and ease of cholinergic neurotransmission to help us understand the properties of sevoflurane, providing us new perspectives for the prevention of sevoflurane-induced cognitive impairment.

NLRP3 inflammasome inhibition by histone acetylation ameliorates sevoflurane-induced cognitive impairment in aged mice by activating the autophagy pathway

Age-related cognitive impairment is associated with diminished autophagy and progressively increased neuroinflammation. Histone acetylation has been shown to be a key process in sevoflurane-induced neurobehavioral abnormalities. Here, we investigated whether histone acetylation regulates the interaction between autophagy and the NLRP3 inflammasome in models of sevoflurane-induced cognitive impairment and explored the underlying molecular mechanisms. Aged C57BL/6 J mice and cultured primary hippocampal neurons were exposed to 3% sevoflurane for 2 h. Hippocampal tissue samples and hippocampal neurons were harvested. The processes of histone acetylation and autophagy and the activation of the NLRP3 inflammasome were observed using western blotting, immunofluorescence staining, and transmission electron microscopy. Suberoylanilide hydroxamic acid (SAHA), an inhibitor of histone deacetylases, increased histone H3 and H4 acetylation in both the mouse hippocampus and primary neurons. Concomitantly, sevoflurane upregulated components of the NLRP3 inflammasome (NLRP3, cleaved caspase-1, and IL-1β) by promoting autophagic degradation in the aging brain. Cognitive deficits and inadequate autophagy induced by sevoflurane were reversed and NLRP3 inflammasome activation was inhibited by SAHA. Treatment with 3-MA, an autophagy inhibitor, eliminated the neuroprotective effects of SAHA on improving cognition in mice, activating autophagy and downregulating the NLRP3 inflammasome. Based on these results, histone acetylation activates autophagy plays an important role in inhibiting the activation of the NLRP3 inflammasome to protect the host from excessive neuroinflammation and sevoflurane-induced cognitive dysfunction in the aging brain.

Caffeine-related effects on cognitive performance: Roles of apoptosis in rat hippocampus following sleep deprivation

Caffeine is a common stimulant widely existed in food and has stimulatory effects on the central nervous system, shift-work individuals often rely on caffeine to maintain attention and keep awake. Although sleep deprivation (SD) is widely considered as an independent risk factor for cognition retardations, however, little is well understood about the synergistic role of caffeine dosage and SD for cognitive performance. This research intended to investigate the underlying molecular mechanism of varying caffeine doses on cognitive function after sleep deprivation. The results revealed that SD attenuated the cognitive dysfunction, associated with ultrastructure damage and pyramidal neuron loss in the hippocampus, decreased in the level of VIP and AVP. SD also significantly accelerated the neuropeptide-associated apoptosis in the hippocampus, which may modulate via the cAMP-PKA-CREB signal path axis and activation of the downstream apoptosis genes. Additionally, the data indicated that low-dose caffeine (LC) contributed to cognitive enhancement, and high-dose caffeine (HC) aggravated cognitive impairment by modulating hippocampal neuronal apoptosis. Our studies suggest that caffeine, particularly in high dosage, may be a potential factor to influence the neurocognitive outcome caused by sleep loss, and the appropriate amount of caffeine ingested after sleep deprivation deserves serious consideration.

Largazole is a Brain-Penetrant Class I HDAC Inhibitor with Extended Applicability to Glioblastoma and CNS Diseases

Largazole is a potent class I selective histone deacetylase inhibitor prodrug with anticancer activity against solid tumors in preclinical models. Largazole possesses in vitro activity against glioblastoma multiforme (GBM) cells and sufficiently crosses the blood-brain barrier based on measurement of the active species, largazole thiol, to achieve therapeutically relevant concentrations in the mouse brain. The effective dose resulted in pronounced functional responses on the transcript level based on RNA sequencing and quantitative polymerase chain reaction after reverse transcription (RT-qPCR), revealing desirable expression changes of genes related to neuroprotection, including Bdnf and Pax6 upregulation, extending the applicability of largazole to the treatment of brain cancer and neurodegenerative disorders. The largazole-induced modulation of Pax6 unifies both activities, since Pax6 expression suppresses GBM proliferation and invasion and inversely correlates with GBM tumor grade, while it is also implicated in neurogenesis, neuronal plasticity, and cognitive ability. Our results suggest that largazole could be repurposed for diseases of the brain.

Irisin ameliorates the postoperative depressive-like behavior by reducing the surface expression of epidermal growth factor receptor in mice

Postoperative depression is a serious problem with under-optimized treatment. Our previous result demonstrated that single dose of propofol exposure in mice could cause depressive-like behavior. In the present study, we explored the possible preventive strategy that could ameliorate the depressive-like behavior in mice. Irisin was used for co-treatment with propofol in mice to test whether irisin could prevent the depressive-like behavior in mice. We found irisin could significantly reduce the immobility time in tail suspension and forced swimming tests in mice with propofol. We also found irisin was able to protect neurons against high concentration propofol treatment induced cell death in cultures. Meanwhile, irisin could significantly inhibit the increase of cytokines in astrocyte cultures exposed to propofol. These in vitro results suggested that interaction between astrocyte and neuron may be involved in the action mechanism that irisin prevented the mice from developing of depressive-like behavior. Last, we revealed that propofol caused increased surface expression of epidermal growth factor receptor (EGFR) but irisin could reduce the expression level of EGFR on cell surface.